DTC P1350: Ic Circuit Open: Notes

PCM provides Ignition Control (IC) spark timing on circuit. PCM correctly calculates optimum spark timing based on inputs received from several engine sensors. Engine load is calculated from MAF sensor, engine RPM is derived from 3X crankshaft position sensor, engine operating temperature from ECT and IAT sensors, and engine knock activity from knock sensor. Other engine functions modify spark to a lesser degree such as TCC engagement and EGR activity.

By-pass circuit controls an internal switch in electronic Ignition Control Module (ICM). By-pass circuit will have 5 volts applied to it unless vehicle is in backup spark (base timing mode). This 5 volt signal from PCM allows a solid state switch to direct IC timing pulses to ICM for sequencing and energizing coil packs. If by-pass circuit is not energized, IC pulses from ICM are shunted to ground, and electronic ICM uses it's own base timing schedule to time and energize coil packs. Code P1350 will set when the following conditions are present.

• IC pulses are detected on IC circuit when vehicle is in by-pass (no voltage applied to by-pass should allow IC pulses to be grounded by electronic ICM). Test will either pass or fail within first 100 milliseconds of engine running. If test passes, test will not run until next key cycle.
  NOTE: Test numbers refer to numbers on diagnostic chart.

1. This test confirms Code P1350 is present and conditions necessary to set Code P1350 exist.
2. Checks for normal IC ground path through ICM. Code P1350 indicates PCM has detected an open or short to voltage in IC circuit, or a short to voltage in by-pass circuit. An IC circuit shorted to ground will also read less than 500 ohms. However, this should cause Code P1350 to set.